The odd one out - Orthographic oddball processing in children with poor versus typical reading skills in a fast periodic visual stimulation EEG paradigm

The specialization of left ventral occipitotemporal brain regions to automatically process word forms develops with reading acquisition and is diminished in children with poor reading skills (PR). Using a fast periodic visual oddball stimulation (FPVS) design during electroencephalography (EEG), we examined the level of sensitivity and familiarity to word form processing in ninety-two children in 2nd and 3rd grade with varying reading skills (n = 35 for PR, n = 40 for typical reading skills; TR). To test children's level of "sensitivity", false font (FF) and consonant string (CS) oddballs were embedded in base presentations of word (W) stimuli. "Familiarity" was examined by presenting letter string oddballs with increasing familiarity (CS, pseudoword - PW, W) in FF base stimuli. Overall, our results revealed stronger left-hemispheric coarse sensitivity effects ("FF in W" > "CS in W") in TR than in PR in both topographic and oddball frequency analyses. Further, children distinguished between orthographically legal and illegal ("W/PW in FF" > "CS in FF") but not yet between lexical and non-lexical ("W in FF" vs "PW in FF") word forms. Although both TR and PR exhibit visual sensitivity and can distinguish between orthographically legal and illegal letter strings, they still struggle with nuanced lexical distinctions. Moreover, the strength of sensitivity is linked to reading proficiency. Our work adds to established knowledge in the field to characterize the relationship between print tuning and reading skills and suggests differences in the developmental progress to automatically process word forms.

Progress in elementary school reading linked to growth of cortical responses to familiar letter combinations within visual word forms

Learning to read depends on the ability to extract precise details of letter combinations, which convey critical information that distinguishes tens of thousands of visual word forms. To support fluent reading skill, one crucial neural developmental process is one's brain sensitivity to statistical constraints inherent in combining letters into visual word forms. To test this idea in early readers, we tracked the impact of two years of schooling on within-subject longitudinal changes in cortical responses to three different properties of words: coarse tuning for print, and fine tuning to either familiar letter combinations within visual word forms or whole word representations. We then examined how each related to growth in reading skill. Three stimulus contrasts-words versus pseudofonts, words versus pseudowords, pseudowords versus nonwords-were presented while high-density EEG Steady-State Visual Evoked Potentials (SSVEPs, n = 31) were recorded. Internalization of abstract visual word form structures over two years of reading experience resulted in a near doubling of SSVEP amplitude, with increasing left lateralization. Longitudinal changes (decreases) in brain responses to such word form structural information were linked to the growth in reading skills, especially in rapid automatic naming of letters. No such changes were observed for whole word representation processing and coarse tuning for print. Collectively, these findings indicate that sensitivity to visual word form structure develops rapidly through exposure to print and is linked to growth in reading skill. RESEARCH HIGHLIGHTS: Longitudinal changes in cognitive responses to coarse print tuning, visual word from structure, and whole word representation were examined in early readers. Visual word form structure processing demonstrated striking patterns of growth with nearly doubled in EEG amplitude and increased left lateralization. Longitudinal changes (decreases) in brain responses to visual word form structural information were linked to the growth in rapid automatic naming for letters. No longitudinal changes were observed for whole word representation processing and coarse tuning for print.

Neural specialization to English words in Chinese children: Joint contribution of age and English reading abilities

N1 tuning to words, a neural marker of visual word recognition, develops by an interaction between age and ability. The development of N1 tuning to a second learnt print is unclear. The present study examined the joint contribution of age and English reading abilities to N1 amplitude and tuning to English print in Chinese children in Hong Kong. EEG signals were recorded from 179 children (six to nine years old) while they were performing a repetition detection task comprised of different print stimuli measuring three types of tuning, i.e., coarse tuning (real word versus false font), fine tuning (real versus nonword), and lexicality effect (real versus pseudo word). Children were assessed in English word reading accuracy (EWR) and English sub-lexical orthographic knowledge (EOK). Results indicated that coarse tuning decreased with age but increased with EWR and EOK. Fine tuning uniquely increased with EOK, and the lexicality effect increased with EWR. At last, higher EWR was linked to less right-lateralized coarse tuning in younger children. Taken together, the findings support the visual perceptual expertise account in the L2 context, in that N1 coarse tuning, fine tuning, and lexicality effect are driven by skill improvement.

Neurophysiological Correlates of Reading Difficulties in Elementary School Children

The present study examined the event-related potentials (ERPs) and reading-language skills of elementary school children with and without reading difficulties. Typically developing children showed an N400 effect characterized by significantly larger N400 amplitudes elicited by nonwords than real words. Their meaning processing shown by the N400 systematically differed by lexicality. On the other hand, the N400 effect was absent in children with reading difficultiesExploratory analyses were conducted with the N1 and Late Positive Component. Additionally, the relationships between ERPs and reading-language skills were examined; sight word efficiency and phonemic decoding efficiency accounted for significant variance in the N400 effect.

Lexical and sublexical cortical tuning for print revealed by Steady-State Visual Evoked Potentials (SSVEPs) in early readers

There are multiple levels of processing relevant to reading that vary in their visual, sublexical, and lexical orthographic processing demands. Segregating distinct cortical sources for each of these levels has been challenging in EEG studies of early readers. To address this challenge, we applied recent advances in analyzing high-density EEG using Steady-State Visual Evoked Potentials (SSVEPs) via data-driven Reliable Components Analysis (RCA) in a group of early readers spanning from kindergarten to second grade. Three controlled stimulus contrasts-familiar words versus unfamiliar pseudofonts, familiar words versus pseudowords, and pseudowords versus nonwords-were used to isolate coarse print tuning, lexical processing, and sublexical orthography-related processing, respectively. First, three overlapping yet distinct neural sources-left vOT, dorsal parietal, and primary visual cortex were revealed underlying coarse print tuning. Second, we segregated distinct cortical sources for the other two levels of processing: lexical fine tuning over occipito-temporal/parietal regions; sublexical orthographic fine tuning over left occipital regions. Finally, exploratory group analyses based on children's reading fluency suggested that coarse print tuning emerges early even in children with limited reading knowledge, while sublexical and higher-level lexical processing emerge only in children with sufficient reading knowledge. RESEARCH HIGHLIGHTS: Cognitive processes underlying coarse print tuning, sublexical, and lexical fine tuning were examined in beginning readers. Three overlapping yet distinct neural sources-left ventral occipito-temporal (vOT), left temporo-parietal, and primary visual cortex-were revealed underlying coarse print tuning. Responses to sublexical orthographic fine tuning were found over left occipital regions, while responses to higher-level linguistic fine tuning were found over occipito-temporal/parietal regions. Exploratory group analyses suggested that coarse print tuning emerges in children with limited reading knowledge, while sublexical and higher-level linguistic fine tuning effects emerge in children with sufficient reading knowledge.

Brain Source Correlates of Speech Perception and Reading Processes in Children With and Without Reading Difficulties

Neural correlates in reading and speech processing have been addressed extensively in the literature. While reading skills and speech perception have been shown to be associated with each other, their relationship remains debatable. In this study, we investigated reading skills, speech perception, reading, and their correlates with brain source activity in auditory and visual modalities. We used high-density event-related potentials (ERPs), fixation-related potentials (FRPs), and the source reconstruction method. The analysis was conducted on 12–13-year-old schoolchildren who had different reading levels. Brain ERP source indices were computed from frequently repeated Finnish speech stimuli presented in an auditory oddball paradigm. Brain FRP source indices were also computed for words within sentences presented in a reading task. The results showed significant correlations between speech ERP sources and reading scores at the P100 (P1) time range in the left hemisphere and the N250 time range in both hemispheres, and a weaker correlation for visual word processing N170 FRP source(s) in the posterior occipital areas, in the vicinity of the visual word form areas (VWFA). Furthermore, significant brain-to-brain correlations were found between the two modalities, where the speech brain sources of the P1 and N250 responses correlated with the reading N170 response. The results suggest that speech processes are linked to reading fluency and that brain activations to speech are linked to visual brain processes of reading. These results indicate that a relationship between language and reading systems is present even after several years of exposure to print.

Typical and Atypical Development of Visual Expertise for Print as Indexed by the Visual Word N1 (N170w): A Systematic Review

The visual word N1 (N170w) is an early brain ERP component that has been found to be a neurophysiological marker for print expertise, which is a prelexical requirement associated with reading development. To date, no other review has assimilated existing research on reading difficulties and atypical development of processes reflected in the N170w response. Hence, this systematic review synthesized results and evaluated neurophysiological and experimental procedures across different studies about visual print expertise in reading development. Literature databases were examined for relevant studies from 1995 to 2020 investigating the N170w response in individuals with or without reading disorders. To capture the development of the N170w related to reading, results were compared between three different age groups: pre-literate children, school-aged children, and young adults. The majority of available N170w studies (N = 69) investigated adults (n = 31) followed by children (school-aged: n = 21; pre-literate: n = 4) and adolescents (n = 1) while some studies investigated a combination of these age groups (n = 12). Most studies were conducted with German-speaking populations (n = 17), followed by English (n = 15) and Chinese (n = 14) speaking participants. The N170w was primarily investigated using a combination of words, pseudowords, and symbols (n = 20) and mostly used repetition-detection (n = 16) or lexical-decision tasks (n = 16). Different studies posed huge variability in selecting electrode sites for analysis; however, most focused on P7, P8, and O1 sites of the international 10–20 system. Most of the studies in adults have found a more negative N170w in controls than poor readers, whereas in children, the results have been mixed. In typical readers, N170w ranged from having a bilateral distribution to a left-hemispheric dominance throughout development, whereas in young, poor readers, the response was mainly right-lateralized and then remained in a bilateral distribution. Moreover, the N170w latency has varied according to age group, with adults having an earlier onset yet with shorter latency than school-aged and pre-literate children. This systematic review provides a comprehensive picture of the development of print expertise as indexed by the N170w across age groups and reading abilities and discusses theoretical and methodological differences and challenges in the field, aiming to guide future research.

Dynamic functional brain network connectivity during pseudoword processing relates to children's reading skill

Learning to read requires children to link print (orthography) with its corresponding speech sounds (phonology). Yet, most EEG studies of reading development focus on emerging functional specialization (e.g., developing increasingly refined orthographic representations), rather than directly measuring the functional connectivity that links orthography and phonology in real time. In this proof-of-concept study we relate children's reading skill to both orthographic specialization for print (via the N170, also called the N1, event related potential, ERP) and orthographic-phonological integration (via dynamic/event-related EEG phase synchronization - an index of functional brain network connectivity). Typically developing English speaking children (n = 24; 4-14 years) and control adults (n = 20; 18-35 years) viewed pseudowords, consonants and unfamiliar false fonts during a 1-back memory task while 64-channel EEG was recorded. Orthographic specialization (larger N170 for pseudowords vs. false fonts) became more left-lateralized with age, but not with reading skill. Conversely, children's reading skill correlated with functional brain network connectivity during pseudoword processing that requires orthography-phonology linking. This was seen during two periods of simultaneous low frequency synchronization/high frequency desynchronization of posterior-occipital brain network activity. Specifically, in stronger readers, left posterior-occipital activity showed more delta (1-3Hz) synchronization around 300-500 ms (simultaneous with gamma 30-80 Hz desynchronization) and more gamma desynchronization around 600-1000 ms (simultaneous with theta 3-7Hz synchronization) during pseudoword vs. false font processing. These effects were significant even when controlling for age (moderate - large effect sizes). Dynamic functional brain network connectivity measures the brain's real-time sound-print linking. It may offer an under-explored, yet sensitive, index of the neural plasticity associated with reading development.

Predicting Reading From Behavioral and Neural Measures - A Longitudinal Event-Related Potential Study

Fluent reading is characterized by fast and effortless decoding of visual and phonological information. Here we used event-related potentials (ERPs) and neuropsychological testing to probe the neurocognitive basis of reading in a sample of children with a wide range of reading skills. We report data of 51 children who were measured at two time points, i.e., at the end of first grade (mean age 7.6 years) and at the end of fourth grade (mean age 10.5 years). The aim of this study was to clarify whether next to behavioral measures also basic unimodal and bimodal neural measures help explaining the variance in the later reading outcome. Specifically, we addressed the question of whether next to the so far investigated unimodal measures of N1 print tuning and mismatch negativity (MMN), a bimodal measure of audiovisual integration (AV) contributes and possibly enhances prediction of the later reading outcome. We found that the largest variance in reading was explained by the behavioral measures of rapid automatized naming (RAN), block design and vocabulary (46%). Furthermore, we demonstrated that both unimodal measures of N1 print tuning (16%) and filtered MMN (7%) predicted reading, suggesting that N1 print tuning at the early stage of reading acquisition is a particularly good predictor of the later reading outcome. Beyond the behavioral measures, the two unimodal neural measures explained 7.2% additional variance in reading, indicating that basic neural measures can improve prediction of the later reading outcome over behavioral measures alone. In this study, the AV congruency effect did not significantly predict reading. It is therefore possible that audiovisual congruency effects reflect higher levels of multisensory integration that may be less important for reading acquisition in the first year of learning to read, and that they may potentially gain on relevance later on.

Resting state EEG network modularity predicts literacy skills in L1 Chinese but not in L2 English

EEG network modularity, as a proxy for cognitive plasticity, has been proposed to be a more reliable neural marker than power and coherence in predicting learning outcomes. The present study examined the associations between resting state EEG network modularity and both L1 Chinese and L2 English literacy skills among 90 Hong Kong first to fifth graders. The modularity indices of different frequency bands were highly correlated with one another. An exploratory factor analysis, performed to extract a general modularity index, explained 77.1% of the total variance. The modularity index was positively associated with Chinese word reading, Chinese phonological awareness, Chinese morphological awareness, and Chinese reading comprehension but was not significantly correlated with English word reading or English morphological awareness. Findings suggest that resting state EEG network modularity is likely to serve as a reasonable, reliable, and cost-effective neural marker of the development of first language but not second language literacy skills.

Uncoupled Brain and Behavior Changes in Lexical, Phonological, and Memory Processing in Struggling Readers

Paired behavioral and ERP measures were used to track change over time in 17 third- and fourth-grade struggling readers. Word and nonword reading on standardized tests improved, but differentiation of words and letter strings, measured by N170 and N400 amplitude, did not significantly change. Sound awareness scores improved, but the ERP rhyming effect did not significantly change. Both digit span scores and latency of the P300 oddball effect decreased. Correlations between the ostensibly matched behavioral and electrophysiological measures of change were not significant, indicating that use of ERP and behavioral measures can provide nonoverlapping insight into change during reading development.

Developmental changes in neural letter-selectivity: A 1-year follow-up of beginning readers

The developmental course of neural tuning to visual letter strings is unclear. Here we tested 39 children longitudinally, at the beginning of grade 1 (6.45 ± 0.33 years old) and 1 year after, with fast periodic visual stimulation in electroencephalography to assess the evolution of selective neural responses to letter strings and their relationship with emerging reading abilities. At both grades, frequency-tagged letter strings were discriminated from pseudofont strings (i.e. letter-selectivity) over the left occipito-temporal cortex, with effects observed at the individual level in 62% of children. However, visual words were not discriminated from pseudowords (lexical access) at either grade. Following 1 year of schooling, letter-selective responses showed a specific increase in amplitude, a more complex pattern of harmonics, and were located more anteriorly over the left occipito-temporal cortex. Remarkably, at both grades, neural responses were highly significant at the individual level and correlated with individual reading scores. The amplitude increase in letter-selective responses between grades was not found for discrimination responses of familiar keyboard symbols from pseudosymbols, and was not related to a general increase in visual stimulation responses. These findings demonstrate a rapid onset of left hemispheric letter selectivity, with 1 year of reading instruction resulting in increased emerging reading abilities and a clear quantitative and qualitative evolution within left hemispheric neural circuits for reading.

Electroencephalography decoding of Chinese characters in primary school children and its prediction for word reading performance and development

Research on what neural mechanisms facilitate word reading development in non-alphabetic scripts is relatively rare. The present study was among the first to adopt a multivariate pattern classification analysis to decode electroencephalographic signals recorded for primary school children (N = 236) while performing a Chinese character decision task. Chinese is an ideal script for studying the relationship between neural discriminability (i.e., decodability) of the orthography and behavioral word reading skills since the mapping from orthography to phonology is relatively arbitrary in Chinese. This was also among the first empirical attempts to examine the extent to which decoding performance can predict current and subsequent word reading skills using a longitudinal design. Results showed that neural activation patterns of real characters can be distinguished from activation patterns for pseudo-characters, non-characters, and random stroke combinations in both younger and older children. Topography of the transformed classifier weights revealed two distinct cognitive sub-processes underlying single character recognition, but temporal generalization analysis suggested common neural mechanisms between the distinct cognitive sub-processes. Suggestive evidence from correlational and hierarchical regression analyses showed that decoding performance, assessed on average 2 months before the year 2 behavioral testing, predicted both year 1 word reading performance and the development of word reading fluency over the year. Results demonstrate that decoding performance, one indicator of how the neural system is functionally organized in processing characters and character-like stimuli, can serve as a useful neural marker in predicting current word reading skills and the capacity to learn to read.

Visual word form processing deficits driven by severity of reading impairments in children with developmental dyslexia

The visual word form area (VWFA) in the left ventral occipito-temporal (vOT) cortex is key to fluent reading in children and adults. Diminished VWFA activation during print processing tasks is a common finding in subjects with severe reading problems. Here, we report fMRI data from a multicentre study with 140 children in primary school (7.9-12.2 years; 55 children with dyslexia, 73 typical readers, 12 intermediate readers). All performed a semantic task on visually presented words and a matched control task on symbol strings. With this large group of children, including the entire spectrum from severely impaired to highly fluent readers, we aimed to clarify the association of reading fluency and left vOT activation during visual word processing. The results of this study confirm reduced word-sensitive activation within the left vOT in children with dyslexia. Interestingly, the association of reading skills and left vOT activation was especially strong and spatially extended in children with dyslexia. Thus, deficits in basic visual word form processing increase with the severity of reading disability but seem only weakly associated with fluency within the typical reading range suggesting a linear dependence of reading scores with VFWA activation only in the poorest readers.

Simultaneous EEG and fMRI reveals stronger sensitivity to orthographic strings in the left occipito-temporal cortex of typical versus poor beginning readers

The level of reading skills in children and adults is reflected in the strength of preferential neural activation to print. Such preferential activation appears in the N1 event-related potential (ERP) over the occipitotemporal scalp after around 150–250 ms and the corresponding blood oxygen level dependent (BOLD) signal in the ventral occipitotemporal (vOT) cortex. Here, orthography-sensitive (print vs. false font) processing was examined using simultaneous EEG-fMRI in 38 first grade children with poor and typical reading skills, and at varying familial risk for developmental dyslexia. Coarse orthographic sensitivity was observed as an increased activation to print in the N1 ERP and in the BOLD signal of individually varying vOT regions in 57% of beginning readers. Finer differentiation in processing orthographic strings (words vs. nonwords) further occurred in specific vOT clusters. Neither method alone showed robust differences in orthography-sensitive processing between typical and poor reading children. Importantly, using single-trial N1 ERP-informed fMRI analysis, we found differential modulation of the orthography-sensitive BOLD response in the left vOT for typical readers only. This result, thus, confirms subtle functional alterations in a brain structure known to be critical for fluent reading at the very beginning of reading instruction.

Early Brain Sensitivity to Word Frequency and Lexicality During Reading Aloud and Implicit Reading

The present study investigated the influence of lexical word properties on the early stages of visual word processing (<250 ms) and how the dynamics of lexical access interact with task-driven top-down processes. We compared the brain's electrical response (event-related potentials, ERPs) of 39 proficient adult readers for the effects of word frequency and word lexicality during an explicit reading task versus a visual immediate-repetition detection task where no linguistic intention is required. In general, we observed that left-lateralized processes linked to perceptual expertise for reading are task independent. Moreover, there was no hint of a word frequency effect in early ERPs, while there was a lexicality effect which was modulated by task demands: during implicit reading, we observed larger N1 negativity in the ERP to real words compared to pseudowords, but in contrast, this modulation by stimulus type was absent for the explicit reading aloud task (where words yielded the same activation as pseudowords). Thus, data indicate that the brain's response to lexical properties of a word is open to influences from top-down processes according to the representations that are relevant for the task, and this occurs from the earliest stages of visual recognition (within ~200 ms). We conjectured that the loci of these early top-down influences identified for implicit reading are probably restricted to lower levels of processing (such as whole word orthography) rather than the process of lexical access itself.

N1 lateralization and dyslexia: An event-related potential study in children with a familial risk of dyslexia

The rapid automatic specialized processing of printed words is signalled by the left-lateralization of the N1 component in the visual event-related potential (ERP). In the present study, we have investigated whether differences in N1 lateralization can be observed between Dutch children with and without (a familial risk of) dyslexia around the age of 12 years using a linguistic judgement task. Forty-five participants were included in the ERP analysis, 18 in the low familial risk group without dyslexia, 15 in the high familial risk group without dyslexia, and 12 in the high familial risk group with dyslexia. The results showed that although the N1 peaked slightly earlier in the left hemisphere, the N1 amplitude was right-lateralized in all groups. Moreover, there were no group differences in N1 amplitude or latency, and there was no relationship between reading (related) test scores and N1 characteristics. The results of the present study and our previous findings in adults suggest that print-tuning lateralization is a process that is still developing in adolescence. Because other studies did find N1 lateralization in younger readers with a print versus nonprint contrast, the current results seem to indicate that differences in N1 lateralization also depend on the experimental paradigm.

Orthographic-Phonological Mapping and the Emergence of Visual Expertise for Print: A Developmental Event-Related Potential Study

The N1 effect is an electrophysiological marker of visual specialization for print. The phonological mapping hypothesis (Maurer & McCandliss, 2007) posits that the left-lateralized effect reflects grapheme-phoneme integration. In this event-related potential study, first (age = 7.06 years, N = 32) and third-grade readers (age = 9.29 years, N = 28) were presented with pairs of pseudowords and Armenian character strings in a novel implicit same-different paradigm. To test the phonological mapping hypothesis, stimuli were presented in visual-only and audiovisual conditions. The results demonstrated that tuning for print already emerges in first grade. Moreover, the parallel presentation of auditory stimuli enhanced the N1 effect suggesting a role of orthographic-phonological mapping in the development of specialization for print.

The N170 ERP component differs in laterality, distribution, and association with continuous reading measures for deaf and hearing readers

The temporo-occipitally distributed N170 ERP component is hypothesized to reflect print-tuning in skilled readers. This study investigated whether skilled deaf and hearing readers (matched on reading ability, but not phonological awareness) exhibit similar N170 patterns, given their distinct experiences learning to read. Thirty-two deaf and 32 hearing adults viewed words and symbol strings in a familiarity judgment task. In the N170 epoch (120-240ms) hearing readers produced greater negativity for words than symbols at left hemisphere (LH) temporo-parietal and occipital sites, while deaf readers only showed this asymmetry at occipital sites. Linear mixed effects regression was used to examine the influence of continuous measures of reading, spelling, and phonological skills on the N170 (120-240ms). For deaf readers, better reading ability was associated with a larger N170 over the right hemisphere (RH), but for hearing readers better reading ability was associated with a smaller RH N170. Better spelling ability was related to larger occipital N170s in deaf readers, but this relationship was weak in hearing readers. Better phonological awareness was associated with smaller N170s in the LH for hearing readers, but this association was weaker and in the RH for deaf readers. The results support the phonological mapping hypothesis for a left-lateralized temporo-parietal N170 in hearing readers and indicate that skilled reading is characterized by distinct patterns of neural tuning to print in deaf and hearing adults.

Increasing expertise to a novel script modulates the visual N1 ERP in healthy adults

Neural tuning to print develops when children learn to read and is reflected by a more pronounced left occipito-temporal negativity to orthographic stimuli as compared to non-orthographic false fonts or symbols after around 150–250 ms in their N1, a visual event-related potential (ERP). In adults, initial expertise for a novel script can emerge in less than 2 hours through repeated exposure or training. Here, we aimed to assess changes in the visual N1 related to the process of learning associations between unknown written characters and familiar, spoken syllables or words. Thirty-two healthy literate adults learned to associate a set of foreign characters with either syllables or German words within a single experimental session. EEG was recorded during a visual one-back character repetition detection task in which trained characters, untrained characters and familiar letters were presented before and after the training. A bilateral occipito-temporal increase in the N1 negativity with training was only found for the newly learned characters, but not for the control characters. In conclusion, the present data indicate that expertise to novel characters can be induced by a short character–sound association training and is reflected by a bilateral modulation of the visual N1 amplitude. However, no differentiation was found regarding the comparison of word or syllable training, indicating that the visual N1 most likely reflects gaining expertise driven by phonological associations common to both training types.

Sensitivity to Stroke Emerges in Kindergartners Reading Chinese Script

To what extent are young children sensitive to individual stroke, the smallest unit of writing in Chinese that carries no phonological or semantic information? The present study examined Chinese kindergartners’ sensitivity to stroke and the contribution of reading ability and age to stroke sensitivity. Fifty five children from Beijing, including 28 4-year-olds (M_age = 4.55 years, SD = 0.28, 16 males) and 29 5-year-olds (M_age = 5.58 years, SD = 0.30, 14 males), were administered an orthographic matching task and assessed on non-verbal IQ and Chinese word reading. In the orthographic matching task, children were asked to decide whether two items were exactly the same or different in three conditions, with stimuli being correctly written characters (e.g., “”), stroke-missing or redundant characters (e.g., “”), and Tibetan alphabets (e.g., “”), respectively. The stimuli were presented with E-prime 2.0 software and were displayed on a Surface Pro. Children responded by touching the screen and reaction time was used as a measure of processing efficiency. The 5-year-olds but not the 4-year-olds processed correctly written characters more efficiently than stroke-missing/redundant characters, suggesting emergence of stroke sensitivity from age 5. The 4- and 5-year-olds both processed correctly written characters more efficiently than Tibetan alphabets, ruling out the possibility that the 5 year olds’ sensitivity to stroke was due to the unusual look of the stimuli. Hierarchical regression analyses showed that Chinese word reading explained 10% additional variance in stroke sensitivity after having statistically controlled for age. Age did not account for additional variance in stroke sensitivity after having considered Chinese word reading. Taken together, findings of this study revealed that despite the visually highly complex nature of Chinese and the fact that individual stroke carries no phonological or semantic information, children develop sensitivity to stroke from age 5 and such sensitivity is significantly associated with reading experience.

Top-down modulation of early print-tuned neural activity in reading

Fast neural tuning to print has been found within the first 250ms of stimulus processing across different writing systems, indicated by larger N1 negativity in the ERP to words (or characters) compared to control stimuli, such as symbols. However, whether print tuning effects can be modulated by task demands at early stages of visual word recognition is still under debate. To further explore this issue, an ERP study in Chinese was conducted. Familiar, high-frequency, left/right-structured Chinese characters and unfamiliar, stroke number-matched symbols (Korean characters) were used as stimulus conditions. While viewing the characters and symbols, 20 native Chinese speakers performed three tasks: delayed naming, repetition detection, and blue color detection. Results from occipito-temporal and whole map analyses suggest that the influence of task on print tuning changes throughout the N1. Accordingly in the N1 onset, a print tuning main effect was found, with a stronger N1 to words than symbols, irrespective of task. In the N1 offset, a print-by-task interaction reflected a more negative N1 to symbols than words in both delayed naming and color detection, but not in the repetition detection. After the N1 an N2 was observed with task and condition main effects at the whole map level. Taken together, the current study provides evidence that neural tuning to print is modulated by task demands already within the first 250ms, suggesting that early visual-orthographic processing may be less automatic than it was thought, and the possible top-down modulation may be much faster than it was previously assumed.

Event-related potential evidence in Chinese children

Visual word N170 is an index of perceptual expertise for visual words across different writing systems. Recent developmental studies have shown the early emergence of visual word N170 and its close association with individual’s reading ability. In the current study, we investigated whether fine-tuning N170 for Chinese characters could emerge after short-term literacy learning in young pre-literate children. Two groups of Chinese preschool children were trained for visual identification and free writing respectively. Results showed that visual identification learning led to enhanced N170 sensitivity to characters over radical-combinations in the left hemisphere and line-combinations in the right hemisphere, and writing learning led to enhanced N170 sensitivity to characters over radical-combinations and line-combinations in the right hemisphere. These results suggested that the N170 component became more sensitive for the local graphic feature (strokes) of characters rapidly after brief literacy learning even in young children; and writing learning experiences specifically led to enhanced orthographic sensitivity in the right hemisphere.

Selectivity of N170 for visual words in the right hemisphere: Evidence from single-trial analysis

Neuroimaging and neuropsychological studies have identified the involvement of the right posterior region in the processing of visual words. Interestingly, in contrast, ERP studies of the N170 typically demonstrate selectivity for words more strikingly over the left hemisphere. Why is right hemisphere selectivity for words during the N170 epoch typically not observed, despite the clear involvement of this region in word processing? One possibility is that amplitude differences measured on averaged ERPs in previous studies may have been obscured by variation in peak latency across trials. This study examined this possibility by using single-trial analysis. Results show that words evoked greater single-trial N170s than control stimuli in the right hemisphere. Additionally, we observed larger trial-to-trial variability on N170 peak latency for words as compared to control stimuli over the right hemisphere. Results demonstrate that, in contrast to much of the prior literature, the N170 can be selective to words over the right hemisphere. This discrepancy is explained in terms of variability in trial-to-trial peak latency for responses to words over the right hemisphere.

N1 and P2 to words and wordlike stimuli in late elementary school children and adults

In an investigation of the development of fine-tuning for word processing across the late elementary school years as indexed by the posterior N1 and P2 components of the ERP waveform, third, fourth, and fifth graders and a comparison group of adults viewed words, pseudowords, nonpronounceable letter strings, and false font strings in a semantic categorization task. In adults, N1 was larger to and P2 was later to words as compared to pseudowords, a finely tuned effect of lexicality reflecting specialization for word processing. In contrast, in each group of children, N1 was larger to letter strings than false font strings and P2 was larger to false font strings than letter strings, reflecting coarse encoding for orthography. In regression analyses, scores on standardized behavioral test measures of orthographic knowledge, decoding skill, and fluency predicted N1 amplitude; these effects were not significant with age included as a separate predictor. None of the behavioral scores, in models including or not including age, predicted P2 amplitude. In direct comparisons between groups, there were multiple differences between the child and adult groups for both N1 and P2 amplitude effects, and only a single significant difference between two child groups. Overall, the findings suggest a lengthy developmental time course for the fine-tuning of early word processing as indexed by N1 and P2.

Training by visual identification and writing leads to different visual word expertise N170 effects in preliterate Chinese children

The N170 component of EEG evoked by visual words is an index of perceptual expertise for the visual word across different writing systems. In the present study, we investigated whether these N170 markers for Chinese, a very complex script, could emerge quickly after short-term learning (∼ 100 min) in young Chinese children, and whether early writing experience can enhance the acquisition of these neural markers for expertise. Two groups of preschool children received visual identification and free writing training respectively. Short-term character training resulted in selective enhancement of the N170 to characters, consistent with normal expert processing. Visual identification training resulted in increased N170 amplitude to characters in the right hemisphere, and N170 amplitude differences between characters and faces were decreased; whereas the amplitude difference between characters and tools increased. Writing training led to the disappearance of an initial amplitude difference between characters and faces in the right hemisphere. These results show that N170 markers for visual expertise emerge rapidly in young children after word learning, independent of the type of script young children learn; and visual identification and writing produce different effects.